SMM7 March 15: Chen Hao, Engineering Research Center of the Ministry of Education for efficient Development and Application of Tungsten Resources in Jiangxi University of Technology, brought a lecture on the theme of "preparation of Refractory spherical Powder and Wear-resistant Surface strengthening coating Materials" at the "China Tungsten Industry Market and Application Summit Forum and China cemented Carbide Market Application Symposium". The background of the project, the main technical content, the main innovation, the technical indicators and the application of the results are explained in detail.
Tungsten is a strategic metal, which plays a very important role in many fields, such as aerospace, national defense, electronic information and so on.
Wear and corrosion are the two major damage forms of mechanical parts and engineering components, resulting in amazing economic losses.
High-performance hard surface powder material is an important basis and guarantee for energy saving, emission reduction and consumption reduction, supporting the efficient operation of key core components in metallurgical machinery, mining, coal and other fields.
The WC produced by traditional reduction and carbonization method is polygonal, poor fluidity and low hardness, so it is difficult to meet the requirements of high-precision and cutting-edge fields.
Traditional WC-Co composite powder preparation process
Long process, tedious process and high energy consumption
The carbonization temperature is above 1300 ℃ and the energy consumption is high.
Solid-solid mixture, uneven mixing, easy to introduce impurities
Main technical content
WC material system
WC-Co material system
Plasma surface strengthened coating
Main innovations and achievements
The gas atomization process of ultra-high temperature melt above 2700 ℃ is analyzed, the control model is established, and the atomization mechanism is revealed.
The equal volume spherical WC powder with few surface defects was prepared to solve the problem of preparing fine-grained powder by atomization of ultra-high melting point materials.
WC-Co composite powder
Breaking through the traditional mixing theory of powder materials, a new theory of "ion interlayer mixing" is explored.
Construct the rapid precipitation analysis model and develop the rapid precipitation technology.
Research and development of collaborative in-situ synthesis technology to achieve short-flow preparation of ultra-fine grained WC-Co powder.
The equipment of ultra-high temperature melting and ultra-high temperature atomization is designed and manufactured, which makes it possible for continuous gas atomization of ultra-high temperature melt above 2700 ℃.
The metallurgical bonding coating was obtained by plasma controlled heating in situ reaction and a complete set of equipment was successfully developed. the surface metallurgical control system platform of multi-channel synchronous powder feeding plasma beam was constructed to realize on-line monitoring and rapid optimization of parameters.
The integrated equipment of low temperature in-situ reduction and carbonization is independently developed to realize the continuous operation of multi-process of calcination reduction and carbonization.
It can save the original working procedure of drying and reduction, solve the shortcomings of uneven air flow and temperature, high labor intensity, too much dust, long production cycle and easy oxidation of powder in traditional operation, and increase the production capacity of composite powder by 2 times.
Technical index of WC and WC-Co powder
The main results are as follows: (1) A large number of fine-grained WC powders with high degree of spheroidization, few surface defects and high hardness were prepared by ultra-high temperature atomization, which overcame the defects of polygonal and poor fluidity of WC prepared by casting method. The spherical tungsten carbide powder with good fluidity, fine acicular eutectic structure, microhardness of 3200HV and Hall velocity of 6.5s/50g was prepared.
(2) the tungsten, cobalt, carbon and other elements were uniformly mixed at the molecular level, the composition of the material reached an ideal uniform state, and the problems of uneven mixing and easy introduction of impurities in the traditional solid-solid ball mill were solved. The WC-Co powder material with controllable structure and properties and WC grain less than 400nm was prepared.
Technical index of plasma surface strengthening
The wear-resistant layer is thin, the wear resistance is poor, and the thickness is uneven.
The adhesion with the substrate is poor, and the coating is easy to fall off.
The mechanical properties of the matrix will be changed after spraying.
The surface is easy to adhere to coal ash, which affects the thermal conductivity of the matrix.
Plasma surface metallurgical strengthened coating
There is no need for pre-treatment such as sandblasting and pickling on the surface of metal parts.
Metallurgical combination with the substrate, strong bonding force, not easy to fall off;
The mechanical properties and thermal conductivity of the matrix will not be changed after the coating.
Excellent wear-resistant protection, surface hardness > HRC 72;
The thickness of wear-resistant layer is uniform;
The microstructure of the coating is uniformly distributed and the internal grain adhesion is strong.
The thickness of the coating can reach 0.2~5mm.
Technical index of plasma surface strengthened coating
The project has been applied in Jiangxi, Hunan and Shandong enterprises, forming an industrial scale with an annual output of 200 tons of composite powder and 150 sets of powder metallurgy equipment production lines.
Using the developed WC and WC-Co as raw materials, a series of products are developed and applied by means of plasma surface strengthening treatment and increasing material manufacturing, in which the service life of the scraper conveyor is increased by 5 times, the transportation efficiency is increased by more than 30%, and the cutter with ultra-thick wear-resistant coating is developed, which is 5 times longer than that of the ordinary cutter. The service life of the developed coating scraper with wear-resistant coating is increased by 5 Mel by 8 times, which meets the needs of efficient continuous production in harsh environment.
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